OBJECTIVE:
To determine the validity of oral hygiene questions for children, as commonly
used in epidemiological studies, and assess their validity by family income
and mother's education.METHODS: A subsample of 1122 children from the 2004 Pelotas Birth Cohort,
Southern Brazil (who had participated in a 2009 oral health study) was analyzed.
The children received dental examinations, and their mothers were interviewed
at home. The gold standard for oral hygiene was the Simplified Oral Hygiene
Index; from its total score, the outcome was dichotomized into the absence (total
score = 0) or presence (total score > 1) of dental plaque. The mothers
answered questions related to their child's oral hygiene, including daily toothbrushing,
toothbrushing before sleeping and the combination of the two (oral hygiene).
These responses were dichotomized into regular and irregular. The validity was
determined by calculating the percentages and respective 95% confidence intervals
for sensitivity, specificity, positive predictive value and negative predictive
value.RESULTS: The overall prevalence of dental plaque was 37.0%. The following
sensitivities, specificities, positive predictive values and negative predictive
values were observed: 29.6%, 82.5%, 49.8% and 66.6%, respectively, for irregular
daily toothbrushing; 41.8%, 64.6%, 40.9% and 65.5%, respectively, for irregular
toothbrushing before sleeping; and 48.8%, 60.8%, 42.2% and 67.0%, respectively,
for irregular oral hygiene. The validity of the oral hygiene reporting varied
across different levels of family income and mother's education. The sensitivity
and positive predictive values were higher among children with lower incomes
and less educated mothers, while opposite associations were observed for specificity
and negative predictive value.CONCLUSIONS: Oral hygiene questions answered by mothers of five year-old
children are not an appropriate substitute for direct oral hygiene assessment
by the clinical examination of dental plaque.

Estimates of health-outcome
prevalence measures based on self-reported measurements present advantages,
such as simplicity, time-efficiency and low information cost; these advantages
have justified using self-reporting in population surveys.14 Thus,
incorporating oral health questionnaires into epidemiologic studies has become
more common, as evidenced by the US National Health and Nutrition Examination
Survey2 and by Brazilian studies, such as the Pesquisa do Sistema
de Vigilância de Fatores de Risco e Proteção para Doenças
Crônicas por Inquérito Telefônico 2009 (VIGITEL- System
of Risk Assessment and Protection against Chronic Diseases by Telephone Survey
-)ª and the Suplemento em Saúde
da Pesquisa Nacional por Amostra de Domicílio 2008 (PNAD - National
Survey by Domiciliary Sampling - Health Supplement).b

However, such strategies
will only be useful if the questions are valid, i.e., if the individual self-assessment
actually matches the epidemiological diagnose in most of the cases. In Brazil,
researchers have investigated the validity of self-reported weight and height,21
as well as diagnoses for hypertension5 and diabetes.13
These measures have been used to assess morbidity in population surveys and
have demonstrated adequate accuracies.

In the oral health
field, some studies have also focused on this theme. Evidence from the literature
has indicated that the validity of some self-reported measures of gingivitis
and periodontal disease,3 the presence of dental caries,17
restorative needs18 and orthodontic needs23 are undesirably
low, whereas tooth counts and the use of partial dentures15 show
acceptable validities. All of the oral health studies mentioned above were performed
in adolescent, adult and elderly populations in developed countries. The validity
of self-reported oral health measures in children has been poorly addressed,11
and studies of this nature have not been performed in developing countries.

Childhood is a
critical period for acquiring knowledge and habits, where these may subsequently
affect health and behavior patterns.4 Bacterial plaque control is
recognized as a key factor for preventing dental caries, gingivitis and periodontitis,
and it can be used to assess oral hygiene standards. Furthermore, such an assessment
may aid in planning preventative and health-promotion educational programs,
which commonly target schoolchildren. In addition, it has been shown that oral
hygiene standards in children are influenced by their socioeconomic factors
and parents' attitudes towards oral health.12

Clinical-epidemiological
indicators, such as the Simplified Oral Hygiene Index (OHI-S) proposed by Greene
& Vermillion (1964),9 have traditionally been used to assess
the oral hygiene levels of individuals or communities. Classic oral hygiene
questions, such as the frequency of daily toothbrushing, have been extensively
used in research and population surveys to assess oral hygiene levels and, in
some instances, as substitutes for clinical examinations.11 However,
the validity of such questions is not currently known, which makes them weak
from a scientific point of view and compromises their use.

The aim of this
study was to determine the validity of questions commonly used in epidemiological
studies of children's oral hygiene to predict the presence of dental plaque,
comparing overall validity with the results obtained by subgroups of socioeconomic
status.

METHODS

This study used
data obtained from an oral health study nested in the 2004 Pelotas Birth Cohort
(Brazil). The mothers of all the children born in the urban zone of the town
of Pelotas in 2004 were identified and invited to participate in this cohort
study. Approximately 99% of the 4,558 eligible children were included in the
study soon after their births. At three months of age, the follow-up rate dropped
to 96%, at 12 months to 94%, at 24 months to 93.5% and at 48 months to 92%.
Further details of the cohort study's procedures can be found in the report
by Barros et al (2006).1

The oral health
study commenced in August 2009. The parents/guardians of all the cohort members
born between September and December of 2004 who had been followed up to the
age of four years (n=1303) were invited to participate in the study. The children
were aged five (plus or minus a few weeks) and were in the deciduous stage of
dentition (the scope of this study),22 as defined by the World Health
Organization's (WHO) criteria for epidemiological oral health studies.

A team of eight
dentists and eight interviewers performed the fieldwork, which consisted of
oral examinations for dental caries, occlusal problems, soft tissue lesions,
the eruption patterns of first permanent molars and the presence of dental plaque.
The tested questions were presented in a structured interview with the mother
that involved questions related to the child's oral hygiene pattern. Information
on the socioeconomic status of the family was obtained during a subsequent follow-up
of the cohort. Both the intraoral examination of the child and the interview
with the mother were performed in a single home visit. The interview preceded
the intraoral examination so that the questionnaire responses would not be influenced
by the outcome of the examination.

Prior to the domiciliary
visits, the dentists underwent training and calibration with 100 children of
the same age (who were not included in the study sample). Dental caries were
recorded using the index of decayed, missing and filled surfaces, according
to the WHO diagnostic criteria.22 The children's oral hygiene status
was assessed using a version of the OHI-S9 that had been modified
to address deciduous dentition. The diagnostic reproducibility of all the conditions
and variables in the study was assessed using simple and weighted kappa statistics;
the intraclass correlation coefficient was also calculated. For dental caries,
the lowest intraclass coefficient obtained was 0.93. The training for the dental
plaque scoring was provided via a theoretical discussion that was illustrated
with images of the various degrees of the condition. Because a plaque examination
and gingival bleeding assessment modify the local environment, it was not possible
to analyze their reproducibility. The children were examined while seated and
under an artificial light (headlamp). The examiners wore the appropriate protective
clothing and equipment and followed all the relevant health and safety guidelines.

The OHI-S (modified
for deciduous dentition) was used as the gold standard for oral hygiene assessment
in this validation study. The presence of plaque was verified on the buccal
surface of 6 index teeth: the upper right second deciduous molar (tooth 55),
the upper right central deciduous incisor (tooth 51), the upper left second
deciduous molar (tooth 65), the lower right second deciduous molar (tooth 85),
the lower left central deciduous incisor (tooth 71), and the lower left second
deciduous molar (tooth 75). According to the OHI-S, dental plaque is defined
as a soft organic material loosely adhering to the tooth surface. The tooth
surface covered by plaque was estimated by visual examination according to the
following criteria: 0 = no plaque present; 1 = plaque covering no more than
1/3 of the surface in question; 2 = plaque covering more than 1/3, but no more
than 2/3 of the surface; 3 = plaque covering more than 2/3 of the surface; 9
= tooth excluded, no information. This last category was considered as missing
data. The total OHI-S score was calculated and later dichotomized into plaque
absent (total score = 0) or plaque present (total score > 1).

The variables on
the child's oral hygiene were answered by the mothers and included: i) daily
brushing frequency, by the question "In general, how many times a day does <child>
brush <his/her> teeth?" The answer choices were never/not every day, once,
twice and three times or more. These were later grouped into irregular (never
or once) or regular (twice or more). ii) brushing before sleeping, by the question
"Before bed, does <child> brush <his/her> teeth?" The possible answers
were never, sometimes and always, which were later grouped into irregular (never
or once) or regular (always). Oral hygiene was defined by the combined frequencies
of daily brushing and brushing before bed. This was categorized as good (regular
brushing frequency and regular bedtime brushing), fair (irregular brushing frequency
and regular bedtime brushing or vice-versa) or poor (irregular brushing
frequency and irregular bedtime brushing). These categories were later narrowed
into irregular (poor and fair) and regular (good). The categorization of oral
hygiene into regular and irregular patterns followed guidelines from the literature.20

The analyses were
performed according to the family income at the child's birth, which was categorized
into quartiles. In addition, the education level of the mother was based on
completed school years and categorized as 0 to 4, 5 to 8, 9 to 11 and 12 or
more years.

The data were entered
twice into the EpiInfo 6.04 statistical software and checked for consistency.
The statistical analysis was performed using Stata 11.0. Absolute and relative
frequencies were extracted for each variable. Plaque prevalence with its 95%
confidence interval (95%CI) for each subgroup was presented according to the
studied variables. The validity was determined by comparing the mother's report
of the child's oral hygiene with the clinical examination findings by the dentists
and calculating the percentage values and respective 95%CI for sensitivity (SE),
specificity (SP), positive predictive value (PPV) and negative predictive value
(NPV). The SE consisted of the fraction of children with dental plaque (according
to the gold standard) whose mothers reported an irregular oral hygiene pattern.
The SP was obtained from the proportion of plaque-free children whose mothers
reported a regular oral hygiene pattern. The PPV was obtained from the proportion
of children with plaque (the true positives) whose mothers reported an irregular
oral hygiene pattern. The NPV was obtained from the proportion of plaque-free
children (true negatives) whose mothers reported a regular oral hygiene pattern.

The project was
approved by the Ethics Committee of the Federal University of Pelotas (process
number 100/2009 on 29/06/2009). Informed consent was obtained from all of the
participants' mothers.

RESULTS

The questionnaire
response rate for this study was 86.6% (n=1129). The final sample included only
those subjects who also underwent the clinical examination for dental plaque
(n=1122).

The distribution
of the studied variables, the prevalence of dental plaque according to sex,
skin color and the child's oral hygiene pattern (as reported by their mothers),
the family income and the mothers' education levels are shown in Table
1. Just over half (52.3%) of the children were boys, and the majority were
white (66.7%). Approximately 80% of the mothers reported that their children
brushed their teeth twice or more per day; however, 42.7% of the children presented
oral hygiene pattern considered irregular. The global prevalence of dental plaque
was 37% (95%CI 34.1;39.9); it was higher among those with an irregular daily
brushing pattern (49.8%, 95%CI 43.5;56.1) and irregular oral hygiene (42.2%,
95%CI 37.7;46.6) than among those in the regular categories. The prevalence
of dental plaque were higher in children with families in the lowest income
quartile (40.8%, 95%CI 35.0;46.5) and less educated mothers (47.2%, 95%CI 39.0;55.5)
than in those with higher income (27.3%, 95%CI 21.6;33.0) and 12 or more years
of education (22.0%, 95%CI 14.0;29.4).

The validity in
relation to the OHI-S of the maternal reporting of the children's oral hygiene
patterns is presented in Table 2. A low
SE was observed for irregular daily brushing (29.6%, 95%CI 25.3;34.3); but when
bedtime brushing was also considered (the variable denominated oral hygiene),
the sensitivity increased to 48.8% (95%CI 43.9;53.7). The opposite occurred
with the SP values, which showed higher values in the irregular daily brushing
group (82.5%, 95%CI 79.5;85.2) and lower values for the oral hygiene variable
(60.8%, 95%CI57.1;64.4). The brushing frequency variable had the highest PPV
(49.8%, 95%CI 43.4;56.2), while the NPV for all three variables showed similar
values, ranging from 65.0% to 67.0%.

Table
3 shows the validity of the oral hygiene patterns in relation to family
income. The assessment of each question varied according to the level of family
income. For all three variables, the SE values for the oral hygiene patterns
reported by the mothers were higher among the individuals with lower family
income. The oral hygiene variable was more sensitive than each of its components
assessed separately. The proportion of children with plaque who were reported
to have an irregular oral hygiene pattern was 54.8% (95%;CI 54.2;64.1) among
those with lower family income, compared to 32.3% (95%CI 21.2;45.1) for those
with a higher family income. However, the specificity of the questions increased
with family income, particularly in the case of brushing frequency. Among the
higher-income families, 69.0% (95%CI 61.5;75.7) of the plaque-free children
were reported to have a regular oral hygiene pattern, and this figure fell to
54.8% in lower-income families (95%CI 45.2;64.1).

The validity results
grouped by the mother's education level (Table
4) followed a pattern similar to that described for family income, i.e.,
higher SE for oral hygiene and higher SP for the frequency of daily brushing
in all the education categories. The increase in the SE for the questions was
inversely proportional to the number of years that the mother attended school,
while the opposite effect was observed for the SP values. The PPV was higher
among the children of less educated mothers, and the contrary was observed for
the NPV.

DISCUSSION

The questionnaire
on oral hygiene patterns, as answered by the mothers of 5-year-old children,
showed an unsatisfactory performance in assessing actual oral hygiene; therefore
its validity as a substitute for the intraoral examination of dental plaque
is questionable. Although no universally accepted criteria for an accurate test
exists, some authors have defined a test to be accurate if the sum of its SE
and SP values is higher than 120%.3 In the present study, despite
using the lowest summation, a desirable level of accuracy was not obtained.

Substituting more
accurate measures for the presence of diseases or conditions by simpler tests,
such as questionnaires, is acceptable, with the understanding that classification
errors may occur. The simpler tests are only useful when the risks are known
and judged low based on a solid assessment of validity using the appropriate
gold standard.8

The results of
the present study must be interpreted with caution because limitations on the
data collection for the gold standard may have occurred. The OHI-S advocates
a visual examination with the aid of a dental probe to determine the extent
of plaque. The use of a plaque-disclosing solution, although not recommended
for epidemiological surveys, could facilitate visualizing the extent of plaque;
this method would thus provide a more accurate diagnosis, with a higher number
of true positives observed. Another relevant point is that the OHI-S originally
assessed the smooth surfaces of the teeth (buccal, palatal or lingual) in up
to 12 readings. The OHI-S was modified in the present study, and only the buccal
surfaces were examined in a total of six readings. Once again, the evaluation
of a lower number of dental surfaces may have reduced the number of true positives
and caused a lower prevalence estimate. Such factors may have reduced the actual
prevalence of dental plaque as identified by the gold standard, which could
consequently have led to a decrease in the PPV for the test questions.

In theory, the
SE and SP of a test are independent from the prevalence of the outcome; in practice,
however, a low prevalence estimate suggests a lower sensitivity and higher specificity
when compared to those obtained from a population with a higher prevalence.8
In the present study, the global prevalence of dental plaque was 37.0%, which
is identical to that found in a preschool population in Belgium7
and is lower than the prevalence reported in other places, such as 83.0% for
pre-school children in Jordan.19 Children with lower-income families,
less-educated mothers12 and irregular oral hygiene habits16
have been found to have higher prevalence of dental plaque, consistent with
findings of this study. The stratification by family income and mother's education
revealed differences in the validity of the questions, which clearly distinguished
the extremes of the strata.

In practical terms,
what really matters is the PPV since it gives the probability of a positive
individual actually having the outcome of interest. The PPV is heavily influenced
by the prevalence of the outcome, unlike the SE or SP.8 According
to this study, the probability of identifying individuals with dental plaque
in children whose mothers have reported an irregular oral hygiene pattern was,
in general, lower than 50%. The prevalence differences between the income and
education groups could explain the variations in performance of the tests used.

The twice-daily
minimum toothbrushing frequency is the most accepted evidence of adequate levels
of oral hygiene. Additional factors, such as brushing time,6 the
use of toothpaste, features of the toothbrush bristles, the use of dental floss,
brushing technique and manual dexterity, can interfere with the efficacy of
good oral hygiene.10 In the case of children younger than six years,
it is recommended that the brushing be performed by an adult until the child
has developed sufficient manual dexterity and cognitive skills to perform their
toothbrushing independently.4 Therefore, children's oral hygiene
is also influenced by their mother's attitudes towards this practice. The low
validity of the oral hygiene questions in this study suggests that toothbrushing
frequency per se is not the best predictor of oral hygiene in children.

Investigating the
validity of self-reported oral health assessments in population surveys is highly
relevant given the high costs of applying more accurate methods of clinical
epidemiological diagnosis, such as intraoral examination. This study showed
a high rate of false positives (52% to 70% overall), which suggests that reports
from mothers on the oral hygiene of their 5-year-old children are not good substitutes
for clinical intraoral examination; therefore, the presence of dental plaque
should be directly assessed. More precise questions should be formulated and
tested in future validation studies.

The authors declare
that there are no conflicts of interests.a Ministry of Health. VIGITEL Brazil
2009. System of Risk Assessment and Protection against Chronic Diseases by Telephone
Survey. Brasília, DF; 2010.b Brazilian Geography and Statistics
Institute. National Survey by Domiciliary Sampling (PNAD). Rio de Janeiro: IBGE;
2008.